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Monday, 02 November 2026
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Physics Past Questions and Answers

Jamb 1985 Physics Questions

Question 26:
When a sound wave passes from air into water its
  • A Speed and frequency increases but its wavelength remains the same
  • B Speed and wavelength increases but its frequency remains the same
  • C Speed decreases
  • D Speed remains the same but its frequency and wavelength change
  • E Speed increases but its frequency and wavelength decreases
View Answer & Explanation
Question 27:
If the fundamental frequency of a closed pipe organ on a day when the speed of sound is 340ms-1 is 170Hz, then the length of the pipe is
  • A 50cm
  • B 70cm
  • C 100cm
  • D 150cm
  • E 200cm
View Answer & Explanation
Question 28:
An object is placed 15cm in front of a concave mirror of radius 40cm. The image formed
  • A Virtual and 60cm behind the mirror
  • B Real and 60cm behind the mirror
  • C Virtual and at infinity
  • D Real and at infinity
  • E Virtual and 40cm from the mirror
View Answer & Explanation
Question 29:
A 45o triangular glass prism can be used as a reflector of light because
  • A A refraction never takes place in such a prism
  • B The angle of reflection equals the angle of incidence
  • C The refractive index of glass is less than 1
  • D It is transparent
  • E The critival angle angle for glass is less than 45<sup style='font-size: smaller;'>o</sup>
View Answer & Explanation
Question 30:
A convex mirror is used as a driving mirror because i. its image is erect. ii. it has a large field of view. iii. it has a long focal length. Identify the CORRECT statement(s)
  • A I andiii only
  • B I and ii only
  • C Ii and iii only
  • D I, ii, and iii only
  • E I only
View Answer & Explanation